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What Causes Turbulence?

For some, turbulence is little more than an annoying disruption during a flight. For others, it’s an absolute nightmare. In all instances, it’s important to bear in mind that turbulence is seldom dangerous, although it can be very uncomfortable. But what causes turbulence? And how do pilots deal with it?

1. Turbulence caused by wind

To put it simply, we have to deal with turbulence if we fly through turbulent air. It’s much like steering a boat through stormy seas. There’s a distinction between high-altitude and low-altitude turbulence. Turbulence close to the ground is often caused by heavy winds. This may be problematic when taking off or landing in stormy weather.

2. Turbulence caused by rising air

At higher altitudes, turbulence arises when air rises vertically – from low to high. This works as follows: the sun warms the earth and the air above it. Hot air expands and rises. This causes what we call an updraft. As the air rises, its temperature drops to dew point. If the air rises further, particles of moisture begin to form in it, creating clouds. And that’s a good thing, because we can now see the turbulence, not only through the cockpit window, but also on our weather radar.

However, if the rising air is very dry, condensation doesn’t form and we can’t see the turbulence. This is known as clear-air turbulence and it’s tricky because it can take us by surprise. The weather radar can’t detect it either, because there are no moisture particles in the air to reflect our radar signals.

Vertical air movement usually stops at high altitude, because the temperatures are very low, which is why we can fly in smooth air above the clouds. Sometimes, however, cumuliform clouds can break through to greater heights. We usually encounter these cumulonimbus clouds in tropical areas, and we do our best to fly around them.

In short, we usually have to deal with turbulence at lower altitudes in our atmosphere. In the old days, before aircraft had pressurised cabins, we had to fly at much lower altitudes, where turbulence was more common.

3. Turbulence caused by jet streams

A jet stream is an extremely strong wind at a higher altitude, reaching speeds of more than 300 km/h (150 knots). These winds mainly blow from west to east in the northern hemisphere, which is why it usually takes longer to fly from Amsterdam across the Atlantic Ocean to North American destinations, than the other way around.

On the outbound flight, we try to avoid the jet stream if we can, because this would mean flying into a headwind. On the homebound flight, we try to take maximum advantage of the tailwind. As a result, a flight from New York to Amsterdam can take up to two hours shorter than the outbound flight.

The tricky thing about a jet stream is that it can suddenly change direction when it encounters high or low-pressure areas. Lots of turbulence can arise in these so-called bends, which are similar to those in a fast-flowing river.

4. Turbulence caused by mountains

If there’s a strong wind, the air may be steered upward when it encounters higher mountains. This may cause waves that can be felt at a high altitude and at a great distance. As a result, we sometimes encounter turbulence when passing over a mountain range.

5. Turbulence caused by an aircraft’s wake vortex

There is also a form of turbulence caused by the aircraft itself. This wake turbulence is similar to that left behind by a big ship passing through water. As a rule, bigger planes result in bigger wakes, and smaller planes are more vulnerable should they run into one. That is why we have rules specifying the minimum distance and interval between two aircraft.

Now you know why a Boeing 737 appears to wait for such a long time on the runway after a wide-body aircraft has taken off.

But what can pilots do?

When preparing for a flight, we always study the weather forecast charts. This allows us to predict whether and where we can expect turbulence.

During the flight, we try to avoid any turbulence we can see from the cockpit or on our radar screens. We also maintain contact with air traffic control and other aircraft in the area to keep abreast of the latest weather conditions.

Unavoidable turbulence

Sometimes air traffic constraints prevent us from avoiding turbulence or we may be surprised by turbulence we cannot see on the radar. That’s when the fasten seatbelt sign goes on and you are urged to take your seat immediately. If it’s really bumpy, we even stop serving passengers and cabin crew have to buckle up as well. That’s important for everyone’s safety.

I’m often asked if turbulence can damage an aircraft. There is little or no chance of this happening. An aircraft is actually quite flexible. I once visited the Boeing plant and saw the wing of a 747 bent upwards several metres in a test structure, only to be released again with a snap. This was repeated again and again, day after day, year after year, and everything remains perfectly intact. So if you’re ever at a window seat and you see the wing moving up and down, don’t worry, it’s made to do just that.

Sounds familiar?

It’s quite possible you’ve heard or read this before. We’ve posted this blog in May, 2016. So this actually is a repost. But let’s be honest: learning more about turbulence never gets old, right? ;-)

ReneThai

Menno Kroon

Janell S

3 years ago

Thank you for this! I will be sharing it with my 10-year old son who will be taking his first flight ever this fall. It is a 12-hour flight and he is very worried about flying. I think this will help him understand it better and be able to relax more.

Laurence

Menno Kroon

Racheal

3 years ago

Interesting post – thank you. One thing I have noticed – it usually gets “bumpy” when flying over the north eastern US and Canada. Over the ocean is fine but the minute you get to the US, it gets noticeably bumpy for a while. I don’t mind too much and information like the above helps a lot. However I still don’t like landing in high wind though – that really can be unpleasant on smaller aircraft…!

Menno Kroon

3 years ago

Hi Robbert, We, pilots, never use the word ‘airpocket’. Indeed sometimes turbulence can be quite severe. It may seem as if we are actually ‘falling’ quite a bit, but I can assure you: This is never the case. Seldom does severe turbulence come completely as a surprise, so hopefully everyone is seated well in advance with the seatbelts fastened.

Menno Kroon

Patricia

Andy

3 years ago

Only when close to the ground usually, but each time it happens and the cause is found it makes flying a little safer. The plane can drop quite a way and injure passages, hence the seat belt sign going on. Only last week around 30 people were jnjured when a plane hit turbulence. If people are not belted in they van be flung from their seats injuring themselves and or other passages. The same goes for the trollies and carry on baggage, another reason service may be stopped and why there are limits to carry on baggage.

A pilot

3 years ago

Dear Patricia,

Very bad turbulance or what we call severe turbulance does not crash an airplane. However, it could be quite uncomfortable for the passengers so make sure if you ever encounter this you keep your seatbelts fastened. Pilots are trained to deal with turbulance, severe turbulance is avoided by using weather radar since it is often accompanied by bad weather and reported so other airplanes can avoid it. Also when turbulance is discovered or expected it is plotted in weather charts which pilots study before their flight. If, however, pilots would encounter severe turbulance, the first thing they would do is to make sure everyone gets seated by putting on the fasten seatbelt sign. Then the airplanes speed is adjusted to the best speed to penetrate this turbulance. Quick shifts in wind direction and speed (called windshear) can be tricky, especially near the ground, therefore there are procedures in place to escape this windshear. The technology to detect these windshears are getting more advanced every day, and therefore safer. To comfort you, the airplane can take a lot more than you think and the pilots are well trained and know what to do, the airplane won’t crash but passengers might bump their heads if their seatbelts aren’t fastened, so make sure you do that and you don’t have to worry about the airplane. Personally I use turbulance to rock me to sleep, in my mind I know we are in good hands and the airpane can take it, so I relax! :) I hope this helps you!

Menno Kroon

Marjolein Straten

3 years ago

Thanks for this information. It is very helpfull as i have followed the training at Stichting Valk to coop with my fear of flying. Turbulence is one of my problemzones during a flight. Although the people at stichting Valk explained everything very well all extra information is nice to understand flying and to learn that turbulence is nothing more than discomfert. I am glad that I get on a plane again (although with some rituals now) and enjoy the beauty of the World. I prefer flights with KLM because the crew is great for people like me. They are very understanding and helpful.

Leon de Groot

3 years ago

Flying as a KLM DC-8 cabin attendant in the early seventies above Africa. I asked the pilots if they liked some coffee to drink. We look well after our flightdeck. We were flying approx. 11 km high and I never saw such big clouds at that altitude. The captain was in contact with flight controle and asked for permission to change direction a bit to avoid that enormous clouds. The captain said, I have great respect for those clouds and do whatever I can to avoid them. So we did.

Adri van den Ouden

Menno Kroon

Carol

3 years ago

What an interesting article. I tend to be very scared on flights when turbulence occurs. Not knowing what’s “behind the scene” makes my head jump into “unreasonable” conclusions.. Very helpful info, It’ll make my next flights less stressful . Thanks!

Menno Kroon

Bernadette Dumont

3 years ago

Thanks for such an informative article. Just curious about one thing does the size of the aircraft dictate how much more severe the turbulence may feel. Eg. if a Boeing 747 and a 737 flies through the same area of turbulence is it felt more in the 737

Menno Kroon

3 years ago

Dear Bernadette, Indeed, if you fly in a smaller plane, you will probably feel more when compared to flying in a much bigger plane. That does not mean that flying in a ‘smaller’ plane is less safe though.

Lavoie Pierre E

Menno Kroon

Mathieu

3 years ago

Let me add my appreciation to this post as well. It was very interesting and I’ve always wanted to know more about this phenomenom. You did a great job of explaining it in easy to understand terms. I have had some white-knuckle experiences with turbulence in my many years of flying, but glad to know of the limited risks and safety issues. Thanks again.

Russell Cruickshank

Menno Kroon

3 years ago

Hi Russell, You’re welcome, I’m glad you enjoyed it. I’m afraid I’m not allowed to advertise for flying with the Catalina. I’m quite sure however, that you will be able to find some info on the internet (-:

Menno Kroon

Doren

3 years ago

Thanks so much KLM for this information. Moments of turbulence can be very unsettling particularly the ones that happen suddenly. it takes so much effort to relax and remind myself that I’m in the hands of God, my maker. I’ll definitely share this information.

Menno Kroon

Martina Bugs

3 years ago

I am very afraid of flying and always try to read as much as I can about safety in aircrafts and specially about turbulence. Nothing helps to calm me down when I am in a airplane and turbulence starts. Last year I flu KLM for the first time and I felt in love with experience onboard. Thank you for this article I will remember it when I fly next week.

Menno Kroon

Luis Avila-Costa

Menno Kroon

3 years ago

Hello Luis, Let me assure you that all aircraft have been designed for a certain ‘lifetime’, which both includes cycles (take off & landings) and flying hours. There is obviously also a big margin. So metal fatigue is normally not a factor to worry about

Fola A

3 years ago

Quite informative KLM. I will forward this information to my husband and some of friends. This detailed information will help a lot of people who are afraid of flying. I have a question about the funny feeling you get in your ears when the aircraft is about to land or take off?

Menno Kroon

3 years ago

Hello Fola, I hope that many people will benefit from reading this article. There really shouldn’t be a reason to be afraid of flying. Regarding your ‘funny feeling’ during landing and take off. That has to do with the cabin pressurization system. Aircraft fly at 10 to 11 km’s of height, while the pressure inside the cabin is equivalent to a height of approximately 1800 meters (depending on the type of aircraft). During take off we start to build up this differential pressure, by closing the so called ‘outflow valves’. Just after landing, when the aircraft is still slightly pressurised, the system automatically opens these valves. That probably gives you the ‘funny feeling’. Nothing to worry about, it is absolutely normal.

Peter ward

3 years ago

Been flying for 20 years (mostly KLM or Delta) and do about 50 flights a year. Still scared stiff of turbulence. My heart races. But still get on that plane because a) for my work and b) it gets me to wonderfull places around the world. The cabin crew on the KLM fights also are just great. Makes me always wonder why the same level of customer service just seems to be impossible on other airlines, particular US based. So well done and great article!!

Mariana

Menno Kroon

Bonnie J. Laferriere, CTC, DS, SCDWS

3 years ago

This is a great article and helps travelers understand some if the safety issues the flight crew have to deal with during the course of the flight. I am sharing this article with my clients (I’m a Travel Consultant.)

Menno Kroon

Margaret Greyvensteyn

3 years ago

How amazing for once in my life after flying KLM I was not afraid of flying. Reading all about flying and possible dangers I prefer and will always if it is my choice fly KLM. Thanx for this explanatory information……you are the best!

Menno Kroon

Mary Thomas

3 years ago

Thank you so much for this detailed information. I’m a frequent flyer that does not particularly enjoy the turbulence but this article is fantastic. Thank you KLM. You are one of the best airlines out there. Keep up the good work! I will be sharing this with my friends.

Lee Young Gil

Jan

3 years ago

Look what happened last saturday (May 21): flying the Catalina aircraft (PH-PBY) for 30 minutes over the IJsselmeer with three splashes on the water and you, Menno Kroon, at the controls! Thanks, it was a fantastic flight in fine weather and only a little bit of so called light chop while passing the IJsselmeerdyke. Good to meet afterwards during the debriefing. I read your blog with interest and concluded, as a retired aviation met: nice blog explaining quit easy and under-standable to pax how you, pilots, deal with turbulence at the flight deck.

Wilhelmina Paauw Hiemstra

marion mebius- de vries

2 years ago

Hi, Marion here, this is a great article on turbulence. I have a website on the Fear of Flying and I would like to tell you that I share your link on my website and I hope that’s ok with you. I do have a question, I would like to make my website bilingual, could you tell me what you used for the Dutch-English version? That would be a great help.My website is howtogetoverflyingfear.com. Thank you, Marion

Lorraine

Adima Williams Junio

Antigone Oreopoulou

1 year ago

Hello Captain Kroon

Thank you for the detailed article and also about your other articles, which found very informative too. But this post is of great help for me. I fly a lot, but turbulence always gives me white knuckles experience! Along with unstable takeoffs and landings. My last landing was a nightmare with the plane sliding sideways on the landing corridor, probably due to side winds and rain. I would like to ask you, if a sudden, unexpected, not seen turbulence during takeoff and landing can create a plane crash. how the pilots cope with that And how planes during take off and landing are protected from black ice. Once more thank you for all this information. At least I will feel more secure during turbulences on air.

Ingrid A

1 year ago

Thanks for this article. We have chosen to book KLM for our trip to South Africa next year. These will be the longest consecutive flights I have ever taken: Boston, USA-Amsterdam and then Amsterdam-Johannesburg. Crossing six time zones and the equator – 16 hours altogether! Although I know all the usual calming tips (choose a seat near the balance post, breathe, watch the flight attendants, etc.), I always become worried when turbulence hits. This article helps me understand more what is happening. I hope I can relax and enjoy the trip.

Paul Henison

EMUAKPEJEKESSENA

Mathieu

1 year ago

This is one of the best KLM blogs – and I seriously mean that since I read them all and am often disappointed by the quality and content of many of them. However this one is interesting, and not only gives lots of useful information but is really well explained in simple terms for the average person.

A big ‘Thank you’ to the writer; I look forward to more blogs from you.

Ali Qureshi

Frits Kleinen Hammans

1 year ago

Highly informative post, thanks so much. I have been flying quite a lot the last 20 years, and I have the impression that both amount and severity of turbulence has increased in time. Do others share this observation? Is there an explanation? Ie global warming, increased traffic. As always, KLM stands out because they give so much information en route, both from the flight deck as the cabbin crew.